ABSTRACT

The large size of wind turbines has posed many problems, an ideal alternative that is the multi-rotor wind turbine, has received attention. The deployment of a tightly arranged two-rotor floating wind turbine can theoretically improve power generation. Thus, it is high priority to understand in detail the physical mechanisms of aerodynamic and wake interference for different arrangements of two-rotor floating wind turbines. In this study, we investigate in detail the power and wake characteristics of two floating horizontal-axis wind turbines (FHAWTs) arranged side-by-side based on Unsteady Reynolds Averaged Navier Stokes (URANS) model. The aerodynamic and wake characteristics of a twin-rotor floating turbine are compared in detail under surge motion with three different wind directions (0°, 45°, 90°). When the twin rotors are arranged in tandem, the mean power output of the system is reduced by 44%. This study can deliver a scenario for the tight arrangement method of floating wind farms.

INTRODUCTION

The high cost of offshore wind farms has been an obstacle to their rapid development, with standardized costs about 1.8 times higher than those of land-based wind turbines (Zhang et al., 2022). In waters (deep-sea region) further from land, where wind energy reserves are abundant, floating wind turbines are perceived as the primary wind energy capture device, but their costs are even higher. Therefore, it is crucial to take effective measures to cut the cost of offshore wind farms.

To further bring down costs, the capacity factor of wind farms needs to be increased, the power generation efficiency of single wind turbines needs to be improved with a large scale of wind turbines (Noyes et al, 2020). The development of floating wind turbines of large size is also accompanied by many new problems arising, such as the deformation of the blade, the requirements of the production process, installation, transportation, post-maintenance and other corresponding supporting management production technology (Jamieson and Branney, 2014). Apart from that, the presence of the wake effect causes power output losses to reach at least 10%-20% in wind farms (Stevens and Charles, 2017), a value that may also be grossly underestimated.

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